By Ron Cowen
An X-ray outburst from the center of our galaxy is providing compelling new evidence that a monster black hole lurks at the Milky Way’s core.
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The high velocity of stars orbiting near the galactic center had already convinced astronomers of a supermassive black hole. To hold these stars in their orbits, the center must harbor an object equal in mass to 2.6 million suns in a region smaller than the radius of the solar system (SN: 10/7/00, p. 232).